Hmm, there is probably less than a full charge of oil in the compressor, but I would blow it out through a hose disconnect or drain it and then add ester and run a vacuum. I think you can modify that protocol and have success, but I wonder if you still have a vacuum tight , water free system, etc.? Half an oil charge plus 2 lbs of 134a, something like that. In practice, AC is often more like cooking than laboratory chemistry. Let the temperature be your guide.